Fluid leakage meter



l June 7, 1960 w. A. PRINCE FLUID LEAKAGE METER Filed Dec. 20, 1956 .Halal- BIEN EEEIIIB INVENTOR. WILLIAM A. PRI/VCE @War-ww ATTORNEY States nun) LEAKAGE METER William A. Prince, Escondido, Calif., assignor tofGeneral Dynamics Corporation, San Diego, Calif., a corporation of Delaware Filed Dec. zo, 1956, ser. No. 629,585

s claims.v (ci. 73740) This invention relates to leakage meters and more particularly to meters for the measurement of volume of leakage under high pressure and high temperature extremes.

Heretofore leakage meters have been designed to measure rate of flow which, when timed, can be con-` verted into quantity of leakage. In one such device a restriction is placed in the path and the uid movement pushes this partial restriction up a scale which can be read through a glass window. Another measuring device places a restriction within the path so that the fluid tlow must pass through a very small opening. A differential pressure gauge measures the pressure on both sides of the opening to thereby obtain the rate of leakage. Still another device completely restricts the fluid path and has a bypass duid path around the restriction. When the bypass path is also restricted two pressure meters measure the pressure on both sides of the restriction in 'the main path. A diierential reading indicates a leakage on one side or the other of the main restriction. However, these meters operate on a pressure measuring principle and require sucient ow to suspend an indicator under ow pressure or suilcient ow to create differential pressure. This method is not satisfactory, for example, in measuring extremely small amounts of iluid at high pressure and temperature extremes as does the present meter.'

The present invention comprises a leakage volume measuring meter which is capable of measuring extremely small amounts, a fraction of a drop, with a high degree of accuracy at pressures up to 10,000 pounds per square inch. Heretofore, the volume of fluid that leaks from a hydraulic system or component into atmosphere was measured in terms of drops per minute or per cycle of operation as the drops were caught in a beaker. However, the measure of such minute volumes under environmental conditions of pressure and temperature varies with geographical locations. With slow leakage under high temperature the drops vaporize before. they can be measured. Counting Ithe drops is not satisfactory either since a drop is not an exact measurement of Volume. A drop of uid will vary in size according to the object from which it falls. For example, a drop formed on the end of a needle is a great deal smaller than a drop which forms on the bottom of a bowling ball. For this reason, instead of externally measuring the volume of uid that leaks from a component to atmosphere it is better to measure internally the volume that is removed from the system under given conditions of pressure and temperature. This has an additional advantage in that the leakage of a test component may be made at a place remote to the location of the test component. This is especially desirable if the component under extreme environmental conditions is leaking a highly explosive or inammable uid such as liquid-oxygen.

for a meter for measuring minute quantities of iluid leakage.

It is another object to provide for an internal measurement of uid volume leakage under given conditions of pressure and temperature without the actual measurement of fluid leaking from the system into the atmosphere.

Another object is the provision of a uid volume leakage meter wherein the compressibility of the zuid due to pressure, the expansiony of the liuid due to temperature, and the elasticity of the system tubing will not introduce error in the measurement.

Another object is the provision of a iluid leakage measurement device of simple design yet which is highly accurate and dependable in performance.

yOther objects and features of the present invention will be readily apparent to those skilled in the art from the following specification and appended drawings wherein is illustrated a preferred form of the invention, and in which:

:Figure 1 is a simplified schematic showing the principle behind, and operation of, the meter; and

Figure 2 is a cross-sectional view of the preferred embodiment showing the addition of other valves and scales for measurement under pulsating pressures and to prevent the loss of instrument uid, and

Figure 3 is a front view showing the window section and two reading scales.

As shown in Figure l the meter is essentially a U-tube partly filled with a heavy fluid, such as mercury, to formV an irnmiscible separation with the uid in the pressure line to the component being tested. Leakage can be measured by the displacement of the separation fluid.

Columns 10 and 11 from the legs of -the U-tube and column 12, which is a glass capillary tube capable of withstanding extremely high pressures, is used to observe and graduate the displacement. When the valve 13 is open pressure is applied to the test component 14 as well as to both legs 10 and 11 of the U-tube and the separation level remains stationary. When the valve 13 is closed pressure is directed to column 10 only andany leakage in the component 14 will effect a displacement of the separation level. Since the operation depends primarily on the differences in the specific gravities of the immiscible liquids, mercury is used for the instrument (lower) fluid 15, although other liquids are also suitable. To prevent any contamination of Ithe iluid 16 with mercury a lm 17 of liquid ilorochemical, such as liquid Teilon was put between the fluids. This liquid has a specific gravity between the values of these two fluids 15 and 16 and appears to be insoluble in either. It is to be noted that this interfacial separation could be accomplished by other methods.

'Il he mechanical features of the device are quite simple and with the exception of a few innovations the design follows the schematic. As shown in Figure 2 the instrument is contained in a single housing 18 having a ilud inlet 19, a tluid outlet Z1, a drain plug 22, an equalizing or regulating valve 13, a selector valve 23, and a Window section 24, all externally visible. Inlet 19 is connected to column 10 at the top and drain plug 22 is connected to it at the bottom. Columns 10 and 11 are connected at the top by fluid path or passage 26 and at the bottom by iuid path or passage Z7. Columns 10 and 11, -together with passage 27, thus form a by-pass path around valve 13 in path 26. Equalizing valve 13 is operable/to restrict tu'd ow through passage 26 and selector valve 235 is operable to restrict uid ow through passage 27. The;

instrument is zeroed by opening the equalizing valve :1S- Q due to the elasticity of the system tubing. When the valve placement is timed. When theselector valve 23 is closed.

only the. displacement of the. small capillary tube isf measured whereas Awhen valve 23 is opened the Vsimultaneous displacement of vboth columns 11 and y12 is measured, Window section 24 has, two scales, shown in Figure3, for obtaining a displacement reading in'eitherA situation.. A ball check valve. incorporated in column to prevent loss of the instrument fluid in the event of, a rapid openingin the test component. t This check valve comprises an opening-2,8` at th'ej bottom of column 10 and a cooperating ball29 which. rides withincolurnn 10 on` the surface ofthe lower, moredense liquid 15. This ball has a density intermediate the densities of the; heavier liquid andthe lighter uid 16 used in component 14 which is being tested forV leakage. Should the seal in the component'14'suddenly`fail causing excess leakage, the

pressure of iluid 1.6 in column 10 would causethe height of uid 15in column',lll-tofrapidly.decrease'until the ball 29 seats over the smaller opening V28. Tofacilitatel the separation of uids and air inthe capillary tube VcolumnY 12 when the instrument isirst lled asharp. edge nozzle` 31 is provided' at the top; Excess uidlS spilling over the topof column 12 then returns to the bottom of column 11. Itis not necessary Ythat the pressure on theV uid under test be constant. With a pulsating pressure the magnitude of uctuations in the Yreadout column will be a function of lche diameter of column `11. Ordinarily, it is slight and if necessary compensated by reading thetop of the oscillation at the initial and linal readings. The accuracy fviewing iluidA movement, aquantity of immiscible uid of density greater than said test uid in ythe bottom portions of this instrument is very precise andis limited principally by the glass precision bore capillary tube 12 which is oommercially available with bores,Y as low as .0025 inch with a plus or minus tolerance of V.00005 inch.

While this device was'rst used in hydraulic, testing of leakage in pressure chambers and leakage between relatively movable components such as pistons, rotary shafts and other objects, it is a versatile and handy instrument having other applications. In addition to measuring the theoretical AV which appears in many hydraulic formulas, it also may be used to test the expansion of tubing or hose, and some of the characteristics of lluids, including such remote phenomena as viscosity. Because the testing may be done in a place remote from the location of the test component,V its use is especially desir- "F i able in detectingV and measuring leakage of components containing hazardous iluids.

i The utility of this leakage measuring meter can be extended. When mercury 'is used, a plurality of electrical contacts or transducers can be incorporated in the second Y leg to produce an electrical signal proportional to fluid Y have been specically disclosed, it is understood that the v invention is not limited thereto as many variations will,

be readily apparent Ato those' skilled in the artl and the;

)invention istobe given'its` broadest possible interpreta-v tion within the terms ofithe following claims:

' Whatlfclaimisr" 1. Means for measuring fluidquantity leakagel of uid, 'om a 'test component comprising a housing having a of said legs, and selector' valve means between said downwardly extending leg and the other of said upwardly extending leg for selectively connecting and disconnecting said uid .connectiontherebetweem e 2. Means for measv g fluidquantity leakage as in. claim l, said transparent wall having indicia means adjacent thereto for transposing iluidmovement into fluid Y quantity, said indiciav means including an indicatingpscale for use when said Selector valve means is open and another indicating scale -for use when said vselector valve means is closed. Y l I 3. Means formeasuring uidV quantity `leakage as in. claim 1, said, leg having atransparentwall being of smaller cross-sectionalarea than saidfother upwardly extending leg, and hypodermic overflowmeans at the top of said leg ofA smaller area includingV a gravity return path connected toV said other upwardly extending leg for return` of said greater` densityruidl to theV bottom thereof.

4.` A iuidV leakage meter for measuring minute leak- Yage in components under high pressure and temperature.

comprising a housing having a iluid inlet for connection. to a fluid source, a uidoutlet for connection with a test component, a first uid path connecting said inlet to said outlet, said path having means for selectively restricting` fluid low therethrough, a second fluid path connecting said inlet to said outlet, said second path comprising a rst column connected to said inlet, Va second and third column connected to said outlet, all said columns being connected at one end thereof, means for selectively restricting uid passage through said second column, said third column being of small Auniform diameter in a transparent material and indicating means in ksaid thirdcolumn. fwhereby uid movement therein can be observed. v

5. Means for measuring minute quantities of fluid'leakage in a test componentcomprising a housing having an; inlet and an outletV adapted for connection between a uid source under predetermined pressure and said component, a rst fluid path in said housing interconnecting.,A said inlet, andY said Voutlet to permit uid iiow therebetween, regulating means in said rst path for regulating said Huid flow, aV second uid path in said housing connected to said first fluid path on either side of said regulating means, said second fluid path comprising first and second interconnected columns, selector means for connecting and disconnecting said columns as desired, an upstanding high pressure resistantY transparent tube `of very small uniform inner bore communicating between said first column and said outlet, a quantity of irnrniscible liquid of greater density than said uid in said columnsV and said tube and movable therewith during uid movement, said transparent tube providing viewingmeans for Watching movement of said liquid in said tube.

6. A uid leakage'metery comprising a housing having a iluid inlet for connection to a lluidVV source and a iluid outletA for connection with a, test component, a rst fluid path connecting said, inletto said outlet, saidpath havingI means for selectively restricting iluid flow therethrough, a second fluid path connecting saidA inlet to said outlet rsaid second path comprising a rst column connected to saidinlet, asecond. and third,y column, connected to said outlet, said second and third'columns being interconnected at both ends thereof and interconnected with said rst column, said second column having means for selectively restricting uid ow therethrough, a quantity of immiscible liquid in said columns of greater density `than uid being passed to said component, said third column being of small diameter and formed in high pressure resistant transparent material -to permit viewing of uid movement therein.

7. A fluid leakage meter as in claim 6, said second and third columns being substantially upright, said third column having an upper end sharp edge nozzle whereby said immiscible greater density liquid spilling over the top thereof will drain down into said second column.

8. Means for measuring minute leakage quantities of fluid from a test component comprising a housing having a luid inlet for connection to a uid source and a uid outlet for connection with a test component, an opening to provide a fluid path in said housing connecting said inlet to said outlet to permit fluid flow therebetween, valve means in said path selectively operable to prevent uid ow therethrough, and a bypass uid path in said housing around said valve means and connected to said rst named path on both sides thereof, said bypass path containing uid movement indicating means.

References Cited in the le of this patent UNITED STATES PATENTS 283,490 Hyatt Aug. 21, 1883 1,393,942 Chadwell Oct. 18, 1921 1,720,934 Toleik July 16, 1929 1,858,399 Jones May 17, 1932 1,901,432 Bradley Mar. 14, 1933 2,853,874 Mennesson ...v Sept. 30, 1958 FOREIGN PATENTS 1,114,506 France Dec. 19, 1955 

